1. Technical Field of the Invention
The present invention relates generally to a solenoid valve and a fuel injector which may be used to inject fuel into an internal combustion engine for automotive vehicles, and more particularly to an improved structure of a solenoid valve designed to minimizing undesirable loads on parts of the solenoid valve and a fuel injector using the same.
2. Background Art
In general, solenoid valves are used in fuel injectors of internal combustion engines. Such solenoid valves are designed to magnetically energize a stator installed in a housing to attract an armature, lifting up a valve member to open a valve hole. A maximum amount of lift of the valve member is fixed upon installation of the stator within the housing. For example, Japanese Patent First Publication No. 10-122086 discloses such a solenoid valve. FIG. 6 shows one example of conventional solenoid valves for use in fuel injectors. The shown solenoid valve is constructed to be installed in a holder body 113 of a fuel injector. A control valve 106 is press fit within an armature 105. The control valve 106 is disposed slidably in a bearing 110 and moved to open a valve hole 108 formed in a plate 111 when the armature 105 is attracted to a stator 104. The bearing 110 is screwed into the holder body 113 to nip the plates 111 and 112 between the holder body 113 and the bearing 110. The stator 104 is welded at portions, as indicated by A and B, to a casing 114. A retaining nut 102 is screwed on a threaded cylinder 107 of the holder body 113 to hold the casing 114 and a spacer 109 between the end body 101 and the bearing 110, thereby positioning the stator 104 relative to the plate 111. This fixes the interval between the stator 104 and the valve hole 108, thereby setting the maximum amount of lift of the control valve 106.
The positioning of the stator 104 relative to the plate 111, however, requires welding of the casing 114 and the stator 104. The stator 104, thus, needs to be made of a heat resisting material If the stator 104 is positioned in direct contact with the end body 101 and the spacer 109 in order to avoid thermal loads on the stator 104, the compressive pressure produced by tightening the retaining nut 102 acts on the stator 104. The stator 104, thus, needs to be made of material which is tough and hard. Specifically, it is necessary to make the stators 104 of limited materials, which will be disadvantages in increasing the attractive force produced by the stator 104 and which may result in undesirable thermal deformation and physical breakage of the stator 104.
It is therefore a principal object of the invention to avoid the disadvantages of the prior art.
It is another object of the invention to provide an improved structure of a solenoid valve designed to minimize undesirable loads on a stator and a fuel injector using the same.
According to one aspect of the invention, there is provided a solenoid valve which comprises: (a) a housing in which a fluid passage and a valve seat is formed; (b) a valve member disposed in the housing, when resting on the valve seat, the valve member closing the fluid passage, when leaving the valve seat, the valve member opening the fluid passage; (c) an armature connected to the valve member, the armature being movable in the same direction as that of movement of the valve member; (d) a stator attracting the armature to move the valve member, opening the fluid passage; (e) a coil producing an attractive force in the stator electromagnetically when the coil is energized; (f) a pressure-receiving mechanism provided in contact with the housing; (g) a fixing mechanism engaging the housing in contact with the pressure-receiving mechanism to press the pressure-receiving mechanism against the housing; and (h) an engaging mechanism holding the stator in engagement with the pressure-receiving mechanism without transmitting an external force acting on the pressure-receiving mechanism from the fixing mechanism and the housing.
In the preferred mode of the invention, the engaging mechanism includes a holding member which is formed integrally with the pressure-receiving mechanism on a side of a surface of the pressure-receiving mechanism opposite a housing-contacting surface and which has formed therein a groove with which the stator is fitted.
The pressure-receiving mechanism includes a cylindrical member having a flange which is formed on a valve seat side of the holding member integrally with the holding member and which is nipped between the housing and the fixing mechanism.
The stator has formed thereon a portion tapered toward the valve seat. The holding member is made of a cylinder which has an end portion remote from the valve seat, bent inwardly and a shoulder formed on an inner wall thereof, inclined to contact with the tapered portion of the stator.
The engaging mechanism includes a stopper made of cylindrical member which hits on one of the armature and the control valve when the armature is attracted by the stator and which has a damper flange. The stator is made of a hollow cylindrical member in which the stopper is disposed in contact of an end remote from the armature with the damper flange.
According to the second aspect of the invention, there is provided a fuel injector which comprises: (a) a nozzle valve working to open and close a spray hole selectively; (b) a nozzle body supporting the nozzle valve slidably; (c) a pressure chamber formed in the nozzle body, producing therein a fuel pressure working to urge the nozzle valve in a spray hole-closing direction; and (d) a solenoid valve working to control the fuel pressure in the pressure chamber. The solenoid valve includes: (a) a housing in which a fluid passage and a valve seat is formed; (b) a valve member disposed in the housing, when resting on the valve seat, the valve member closing the fluid passage, when leaving the valve seat, the valve member opening the fluid passage; (c) an armature connected to the valve member, the armature being movable in the same direction as that of movement of the valve member; (d) a stator attracting the armature to move the valve member, opening the fluid passage; (e) a coil producing an attractive force in the stator electromagnetically when the coil is energized; (f) a pressure-receiving mechanism provided in contact with the housing; (g) a fixing mechanism engaging the housing in contact with the pressure-receiving mechanism to press the pressure-receiving mechanism against the housing; and (h) an engaging mechanism holding the stator in engagement with the pressure-receiving mechanism without transmitting an external force acting on the pressure-receiving mechanism from the fixing mechanism and the housing.
In the preferred mode of the invention, the engaging mechanism includes a holding member which is formed integrally with the pressure-receiving mechanism on a side of a surface of the pressure-receiving mechanism opposite a housing-contacting surface and which has formed therein a groove with which the stator is fitted.
The pressure-receiving mechanism includes a cylindrical member having a flange which is formed on a valve seat side of the holding member integrally with the holding member and which is nipped between the housing and the fixing mechanism.
The stator has formed thereon a portion tapered toward the valve seat. The holding member is made of a cylinder which has an end portion remote from the valve seat, bent inwardly and a shoulder formed on an inner wall thereof, inclined to contact with the tapered portion of the stator.
The engaging mechanism includes a stopper made of cylindrical member which hits on one of the armature and the control valve when the armature is attracted by the stator and which has a damper flange. The stator is made of a hollow cylindrical member in which the stopper is disposed in contact of an end remote from the armature with the damper flange.
According to the third aspect of the invention, there is provided a solenoid valve which comprises: (a) a housing in which a fluid passage and a valve seat is formed; (b) a valve member disposed in the housing, when resting on the valve seat, the valve member closing the fluid passage, when leaving the valve seat, the valve member opening the fluid passage; (c) an armature connected to the valve member, the armature being movable in the same direction as that of movement of the valve member; (d) a stator attracting the armature to move the valve member, opening the fluid passage; (e) a coil producing an attractive force in the stator electromagnetically when the coil is energized; (f) a stator-mounting member; (g) a pressing member engaging the housing to produce a nipping pressure working to nip the stator-mounting member between the pressure member and the housing; and (h) a stator-holding member holding the stator in the stator-mounting member without subjecting the stator to the nipping pressure produced by the pressure member.
In the preferred mode of the invention, the stator-holding member is disposed in alignment with the stator to urge the stator into constant engagement with the stator-mounting member.
The stator-mounting member is made of a hollow cylindrical member which has a flange which is nipped between a step formed on an inner wall of the pressing member and an end of the housing.
The stator-mounting member has disposed therein the stator. The stator-mounting member has formed on an inner wall thereof a tapered surface. The stator has formed on an outer wall a tapered surface which engages the tapered surface of the stator-mounting member.
The stator-mounting member is made of a hollow cylindrical member which has an end portion bent inward to engage a groove formed on an outer wall of the stator-holding member to hold the stator within the stator-mounting member tightly.